1. Field of the Invention
The present invention pertains to valves. More specifically, it pertains to gate valves. In particular, it pertains to a gate valve suitable for transfer of particulate solid materials such as grain, wood chips, dust, coal or any other type.
2. Description of the Prior Art
Many industrial processes which utilize particulate materials require means for transferring these materials between bins, hoppers, trucks, conveyors and the like. Of course, when material transfer is involved, there is usually some need for being able to terminate transfer or flow of the material from one area of containment to another. Simple sliding plates or gate valves are suitable for many of these systems. However, some processes which utilize particulate materials require that these materials be transferred to an area of relatively high pressure, such as a pressure vessel. In these cases, not only must the valve or other device be able to stop and initiate flow of material, it must also provide a fluidtight seal. Providing a fluidtight seal with particulate materials is more difficult than with fluid materials, since the particulates may come between the valve seat and closure member, preventing proper seating. Furthermore, particulate handling valves are more subject to wear, due to the abrasion of seating surfaces by the particulate material. Thus, operation of such valves is less reliable and maintenance is more costly.
Many fluid-handling gate valves have been developed for reducing friction during movement of the gate or closure member from the open to the closed position. Some sort of wedge construction may be provided so that once the gate reaches the closed position it is wedged into tight sealing engagement with the seat. Examples of such valves may be seen in U.S. Pat. Nos. 2,676,780 and 3,003,742. However, these valves are not entirely suitable for handling particulates. One problem with the use of such valves in particulate handling systems is the collection or build-up of particulates within the valve housing which might impair and eventually prevent operation.